Working machines which are used for loading and unloading, are prone to longitudinal instability when handling loads at height, and/or at distance from a main structure of the machine. At least in Europe, it is a statutory requirement for such machines to be provided with a longitudinal load moment control system which automatically prevents operation of the working arm at least in a manner which could increase the longitudinal instability of the machine beyond a safe limit. It is also a requirement for such machines to have a longitudinal moment indicator to provide a warning to an operator of an impending longitudinal unstable condition.
A longitudinal load movement control system is an essential safety feature particularly where such a machine is used in public places or places where there are workers, such as on the highway or on construction sites. It is also a requirement for such machines which are used for loading and unloading operations that such operations are carried out while the machine is stationary, and that when the machine is travelling on the ground, the working arm when the implement is loaded, is substantially lowered. According to the legislation, the longitudinal load moment control system may be disabled when the working arm is fully retracted.
Where such machines are used in an agricultural context, commonly the surface on which the machine has to travel when being driven from one location to another location, is particularly uneven. Known longitudinal load moment control systems are provided on all working machines regardless of their intended use. It will be appreciated that when a machine provided with such a longitudinal load moment control system is used in an agricultural context i.e. the machine is driven on particularly uneven ground, a longitudinal load sensor of the control system may be subject to transient forces which falsely indicate longitudinal instability, and so the longitudinal load control system may operate automatically to prevent or stop operation of the working arm when this is not required. This false indication can actually lead to an increase in the machine's instability.